Techniques for improving the white base and techniques for controlling gradation in silver halide photographic materials of the type in which a color forming coupler is included in a silver halide photographic emulsion and which are developed using a color developer such as p-phenylenediamine for example are important techniques which dominate picture quality. Methods in which various hydroquinones are used have long been known in connection with the improvement of the white base (the prevention of color fogging) in particular.
For example, the use of mono-(linear chain alkyl)hydroquinones has been disclosed in U.S. Pat. No. 2,728,659 and JP-A-49-106329, and the use of mono-(branched chain alkyl)hydroquinones has been disclosed in U.S. Pat. No. 3,700,453, West German Patent Laid Open 2,149,789, JP-A-50-156438 and JP-A-49-106329. (The term "JP-A" as used herein signifies an "unexamined published Japanese patent application".) On the other hand, di-(linear chain alkyl)-hydroquinones have been disclosed, for example, in U.S. Pat. Nos. 2,728,659 and 2,732,300, British Patents 752,146 and 1,086,208, and in Chemical Abstracts, Vol. 58, 6367h, and di-(branched chain alkyl)-hydroquinones have been disclosed in U.S. Pat. Nos. 3,700,453 and 2,732,300, British Patent 1,086,208, in the aforementioned Chemical Abstract, and in JP-A-50-156438.
The use of various anti-color fading agents is known as a means of improving the storage properties of a colored image. Typical examples of organic anti-color fading agents include hydroquinones, 6-hydroxychromans, 5-hydroxychromans, spirochromans, p-alkoxyphenols, hindered phenols such as bisphenols, gallic acid derivatives, methylenedioxybenzenes, aminophenols, aromatic or aliphatic amines, and ether and ester derivatives wherein the phenolic hydroxyl groups of these compounds have been silylated or alkylated. Furthermore, metal complexes, as typified by the (bis-salicylamidoxymato)nickel complex and the (bis-N,N-dialkyldithiocarbamato)nickel complex, are also known in this connection.
Typical examples of these anti-color fading agents have been disclosed on pages 401-440 of JP-A-62-215272. It is known that the intended purpose can be realized by co-emulsifying these compounds with the couplers, normally at a rate of from 5 to 100 percent by weight with respect to the corresponding color coupler, and adding them to the photosensitive layer.
The use of alkylhydroquinones as agents for preventing the occurrence of color impurity has also been disclosed in British Patents 558,258, 557,750 (corresponding to U.S. Pat. No. 2,360,290), 557,802, 731,301 (corresponding to U.S Pat. No. 2,701,197), 2,336,327, 2,403,721, 2,735,765 and 3,582,333, West German Patent Laid Open 2,505,016 (corresponding to JP-A-50-110337), JP-B-56-40816 and JP-B-56-21145. (The term "JP-B" as used herein signifies an "examined Japanese patent publication".)
In recent years, the required levels with respect to a good white base and gradation control have been increased. The use of compounds of comparatively low molecular weight from among the above mentioned hydroquinones has been suggested in this connection in JP-A-62-239153, JP-A-63-63033 and JP-A-63-80250, and these certainly provide a good white base. However, these compounds give rise to problems in that contamination of the development bath and deterioration of development bath performance occur, because these compounds dissolve out of the photographic material into the color development bath during development processing in continuous processing.
Furthermore, when some of the 2,5-dialkylhydroquinones are used in color photographic materials, as disclosed in JP-B-56-21145, the colored images obtained, and especially the colored images which contain cyan dyes and yellow dyes, are known to have an inferior light resistance and fastness.